


Reflection

by SoloShikigami



Category: Undertale (Video Game)
Genre: Light BDSM, Light Bondage, M/M, Mirror Sex, Mirrors, Rope Bondage, Soul Sex, Underfell Sans
Language: English
Status: Completed
Published: 2016-09-29
Updated: 2016-09-29
Packaged: 2018-08-18 11:04:31
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,507
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8159924
Author URL: https://archiveofourown.org/users/SoloShikigami/pseuds/SoloShikigami
Summary: Sans and Red play out a scene and Red decides to throw in a lesson he's still trying to learn for himself.
Gift for my friend Undertailsoulsex!





	

**Author's Note:**

  * For [undertailsoulsex](https://archiveofourown.org/users/undertailsoulsex/gifts).



                "Are you sure you want to do this?"

                "Y-yeah, I'm sure, why wouldn't I be sure?"

                "Well, the fact that you're shaking and I didn't even touch you yet. Hell, I haven't even invited you upstairs yet."

                "Can't blame a guy for being a little nervous, c-can you?"

                "Sans?"

                "Yeah, Red?"

                A soft clank was heard as sharpened teeth pressed against flat ones.

                "Breathe, just breathe, and everything will be all right."

                Sans nodded. "I know, because I'm with you."

                Red chuckled, taking Sans' hand and squeezing it. "You're full of shit. Come on."

                Red lead his lover upstairs; Papyrus was away to train with Undyne for the day and the two had the house to themselves.

                "You remember your safe word?" Red asked.

                "Uh huh," Sans said.

                "I'll be more upset if you don't use it when you want than if you were to just deal with something you don't like. You got it?"

                "I got it, what makes you think I would deal with something I didn't like?"

                "You're me from another dimension, aren't you?"

                "Kinda, I guess."

                They reached the top of the stairs and Red stopped, turned, grabbed Sans by the lapels of his jacket and pulled him in close.

                "Then I know you better than you know yourself," Red all but growled before pulling Sans in for a rough kiss, his tongue demanding entrance and it was gladly granted.

                After a moment, Red got control of himself again and pulled back.

                "I'm serious, Sans," he murmured.

                Sans nodded. "I promise."

                "Good."

                He took Sans' hand again and lead him to the end of the hallway to his former bedroom. Sans gripped his hand a little tighter than he intended, trying to push down the nervous excitement bubbling in his soul.

                Red opened and door and ushered Sans inside and when he looked around, he could barely contain a small squeak of shock.

                Red and his brother had converted his bedroom into a sensual playroom; the walls were painted dark grey, a four-post bed with soft coverings was in one corner, one of the walls had various hooks and rings at different heights, along the other wall were what looked to Sans as a lot of black, leathery straps with silver grommets and buckles, some paddles, a whip, and a few other things he didn't recognize. There was a small refrigerator and dresser along another wall, and a bit to Sans' discomfort, a lot more mirrors than he expected in such a room.

                "You okay there?" Red asked, putting a hand on his shoulder.

                "Yeah, I think so, I just..." Sans' mind flailed for the right words. "Not sure what I expected, to be honest, but I guess this wasn't it."

                "I get it; Pap and I had discussed it and everything, we worked together on most of it, some of the final additions were a surprise to me, too," Red said, taking a moment to give the room a fond once-over before turning to Sans and pulling him into an embrace. "I hope it’s not too overwhelming for you."

                Sans smiled a little shyly as Red's arms wrapped around him and he put his hands on the other's chest.

                "Nah, I'm ready to start when you are," Sans murmured.

                Red smirked and leaned in to kiss Sans gently, which Sans happily returned.

                But then things shifted. Red's tongue pressed into his teeth as if demanding entrance into his mouth, one hand slipped a little further down his back while the other went to the base of his neck, holding him a bit tighter and Sans could feel him taking control.

                He let him.

                Red pulled on the back of Sans' jacket and Sans straightened his arms behind him so it would slip off. Their mouths parted for a moment so the white shirt could be pulled over Sans' head and it was dropped to the side.

                "Take off your pants and get on the bed," Red ordered.

                Sans gave little more than a shudder and a small nod, reluctant to break contact with Red, but he did as he was told. The bed felt a lot softer than he thought it would, figuring that Red and his brother would have wanted something rougher. He laid on his back, trying to calm the small shakes of nervousness and anticipation.

                Red watched Sans with a genuine smile; Sans was always so attentive to others needs, so much so that he usually put theirs in front of his own. Red had been longing for an opportunity to lavish the kind of attention he wanted to give Sans without getting distracted; Sans was a very good lover and had ways of pushing Red’s buttons before he got a chance. He went over to the dresser where they kept their collection of different lengths and types of rope and made his choice carefully before moving to the bed. He smiled, watching Sans worrying at the covers with one hand, trying to not look at the mirror that was on the ceiling.

                "How are you doing?" Red asked.

                "Fine," Sans said, looking relieved that he had something else to focus on. "Whatcha got there?"

                Red chuckled, dropping the rope on the edge of the bed before ridding himself of his own jacket and shirt.

                "Part of what I promised you," Red murmured, taking one of the lengths of rope and handing it to Sans. "Here. Feel it."

                Sans took the black rope and inspected it. "It's soft," he said.

                "If you use real rope, you risk hurting your partner. Trust me, rope burns tend to suck. It's a good thing Paps knows how to heal a bit."

                Sans almost instinctually pulled his leg away when he felt the silky material being wrapped around his ankle, but Red chuckled and pat his leg reassuringly before tying the rope tightly around the bedpost. Sans pulled experimentally while Red tied his other leg - the rope held him for sure and the soft material was gentle on his ankle.

                "This is almost disconcerting," Sans murmured when Red moved to tie his wrists.

                “Why is that?” Red asked.

                “That you’re doing this so well… and quickly,” Sans’ voice dropped to a low murmur as one arm was rendered helpless and his other quivered as Red wrapped the rope around it.

                “I’m a fast learner,” Red said. Tying off the final knot and moving to kneel at Sans’ side. “How are you doing?”

                Sans swallowed hard and nodded, but said nothing.

                Red looked down at Sans fondly, admiring his body. His bones had a tint of blue in them; the result of his magic being aroused and responding to the situation. Now that he had Sans at his mercy, Red was almost openly drooling at the fact that he could do pretty much whatever he wanted, so he took a moment to just brush his hands down the skeletal body on display before him.

                Sans did his best to relax under the gentle touches. It was difficult, but that was the point of this exercise; he was showing Red that he trusted him completely, even to take away his physical ability to control their lovemaking.

                "So, uh, what's with the mirror?" Sans asked, trying to not stare into it.

                "That was, well, still sort of it, part of one of my lessons," Red murmured. "I have a very poor body image, Sans, and while I know you think there is nothing wrong with the way I look, well, you know how it is sometimes."

                Sans nodded, but winced when Red raked the tips of his fingers across his ribs.

                "Slowly I’m learning that my body can be beautiful, that I’m just fine the way I am, because now when you or the Boss says so, I’m leaning to believe it," Red straddled Sans' pelvis. "It took some time and man, was it awkward as hell at first, but slowly I began to like what I see a little more each time," he chuckled as a few fond memories came to mind and made him shudder pleasantly. "A lot of it was Papyrus' help, of course. I'll show you, though."

                Sans tried to ask for more clarification, but Red distracted him with soft touches punctuated by hard scratches. He leaned down to lick across sensitive areas, soothe harder scratches, Red’s sharp teeth nipped at his ribs and shoulders, even at one point biting his neck, almost hard enough to mark it.

                The magic between the both of them built slowly, when Red felt the familiar beginnings of his cock forming he pressed it into Sans at every opportunity. Sans’ own formed and stood at rapt attention.

                “Red,” Sans groaned.

                “Shh, I got you,” Red murmured, a hand trailing down to grasp it firmly before pumping gently. “You are unbelievably sexy, did you know that?”

                Sans groaned again at the touch, then shook his head at the words.

                “It’s true,” Red chuckled, licking his neck. “Open your eyes and look up, you’ll see.”

                Sans cracked an eye open and looked at the ceiling where the mirror he had been avoiding since learning of its presence showed their reflection. He felt his face heating up, and could see quite clearly how blue it was. He focused more on Red, how he was partially lying on Sans, the blue head of his cock disappearing and reappearing as Red stroked him. He glanced at his own face, taking in how flushed he looked, the look of arousal very clear, and he had to look away.

                Red was right, it was embarrassing.

                Red had been watching Sans’ eyes and he chuckled when he looked away. Red moved so he could kiss him.

                “You’re adorable,” Red murmured against his mouth, then decided he could use a bit of a distraction. “How do you feel? Do you like the way I’m touching you?”

                “Y-yes,” Sans murmured.

                “Should I go faster?” Red sped his hand up a little.

                Sans writhed. “Yes.”

                Red kissed him again. “Mmm, nice to actually see you falling apart slowly like this. Usually, I’m a little occupied.”

                “That so?” Sans murmured.

                “Very much so. You always know how to drive me crazy, not that I mind,” Red’s hand moved a little faster and squeezed him a little harder. “So, it’s nice to return the favor.”

                Sans shuddered but then whined a little as Red stopped, but then Red moved away and he could take a guess what he was going to do next.

                Red looked up and saw Sans watching him.

                “Don’t forget to breathe,” Red said. “Also, look up.”

                Sans couldn’t help looking back up at the mirror and he gasped, watching as Red took his entire length into his mouth. Sans’ eyes screwed shut and he tried to move into Red, but he held him.

                Red glanced up now and then as he worked over Sans, enjoying the little twitches and moans, almost wishing he could grab his head and have his way, but also liking that he could have his way with Sans.

                While he was enjoying what he was doing, he was already thinking of the next step. He had an idea of what he would like to do, he just hoped it wouldn’t be too much for the skeleton he currently had trying to buck into his mouth.

                Sans cried out in protest when Red released him.

                “Something you want, Sans?” Red asked, his fingers drawing a trail from the base of his cock to an entrance that he knew lay a little lower.

                “Anything, please, just… I need you,” Sans moaned.

                “Good.”

                “Wait, where are you going?!”

                Red had slipped off the bed. “I won’t be far.”

                Sans groaned, pulling at the ropes that held him; his whole body felt itchy, he wanted so badly to be free, slam Red up again the wall and have his way with him. He did find something a bit arousing over the fact that he couldn’t. He heard something being dragged across the floor, and he had sunk too much into the soft mattress to really see.

                Then Red was back, grinning over him before bending down to kiss him.

                “We’re going to change positions for you. Can’t have you getting bored.”

                Sans chuckled a bit. “Hard to be bored with you.”

                Red smirked and reached over to pull at the ties on Sans’ wrists. Once they were loosened from the bed poles, he pulled Sans’ arms back and tied them together, wrapping some of the rope across his chest.

                “Uhm, Red? The mirror?” Sans asked.

                Upon sitting up, Sans saw what the noise was; there was a full-length mirror standing at the foot of the bed, and while Sans watched for a moment, focused on the skeleton sitting behind him tying his wrists together, he had to look away when his eyes started trailing over his own body and face.

                “It’s part of the lesson,” Red murmured into the side of his skull, rubbing his shoulders and dropping a kiss to his neck. “It’s okay, I promise.”

                Sans watched Red move to untie the ropes holding his ankles from the posts and let him maneuver him to a new position. Red pulled a pillow over for Sans to lean on as he put him on his knees facing the mirror, though Sans wasn’t too happy with the arrangement, but he knew that Red was trying to teach him something.

                Red ran his hands down the back of Sans’ spine once he was settled in the position he wanted.

                “Relax, it’s okay,” he murmured soothingly. “I’m going to make you feel so good, and you’re going to see how beautiful you are.”

                Sans groaned, turning his face into the pillow.

                Red chuckled, backing off to slip off his pants; his own magic was primed and he was so ready to take Sans. Sans pushed back against him and Red put a hand on his hip.

                “I know, I know,” he said, rubbing his hip gently. “I guess you’re ready then?”

                “Yes, please,” Sans murmured, trying to press back again but finding Red stopped him.

                Red hummed in affirmation before slowly entering him. Sans gasped at the sensation, moaning as he was filled.

                “Ah, Sans, you should see yourself,” Red murmured as he pushed himself in the rest of the way, their hips flush with each other.

                Sans glanced up at the mirror; his face was completely flushed with pale blue, he trailed up his own spine, then up to Red’s face, which was also flushed in his signature red. Sans groaned and looked away again.

                Red chuckled. “You’ll learn. But for now, let’s take your mind off of it.”

                He pulled out halfway before pushing steadily back in, pausing for a moment, then doing it again. Sans groaned at the rhythm, it was too slow for him.

                “More, please, I want more,” Sans murmured.

                “Mm, nope not yet,” Red replied. “I’m enjoying this.”

                Sans whimpered, really feeling how helpless he was; he couldn’t push back, of course his hands were tied, literally, and the only thing he could do was look up into the mirror that he knew was in front of his face.

                Why did it bother him so much? Well, bother wasn’t the right word, but it made him feel odd, but why? He loved nothing more than to watch Red’s face when they had sex, was it so bad to look at his own? Did he really dislike the way he looked?

                Faster thrusting soon brought his out of his thoughts along with wandering hands.

                “I can tell when you’re thinking too much,” Red grunted with the effort of trying to form words. He reached down and pulled at the ropes that bound Sans’ arms, making him sit up, and he reached around to wrap an arm around his ribcage, pressing Sans’ back against his chest. “I want you to see what I see. Open your eyes.”

                The new angle made Sans cry out and he leaned back against Red. He wasn’t sure when his eyes closed, but he really didn’t want to open them.

                “Sans, it’s okay,” Red murmured, kissing the side of his skull as one hand trailed down his ribcage. “Trust me, open your eyes, just for a moment.”

                Sans sighed, trying to calm himself and steady his mind, then he slowly opened his eyes.

                It was still embarrassing to see himself in such a position, but he took in the sight all the same. Red smiled at him, leaning down and nibbling on his neck, Sans could clearly see them joined through their translucent magic, and he almost missed the hand slipping into his ribcage.

                “Red,” Sans gasped, dropping his head back and closing his eyes again.

                “See? Beautiful.”

                Suddenly Sans cried out, his entire body twitched as he felt Red close his hand around his soul, squeezing it a little before rubbing his thumb across the surface.

                “You like that?” Red asked.

                “Y-yes,” Sans gasped out, eyes rolling in his skull.

                “Mmm, good, you should watch yourself while I fuck you,” Red gave a shallow thrust at the same time he pressed harder on the soul. “You wouldn’t want to pass out on me before we’re finished, do you?”

                Sans couldn’t answer, but he blinked, his eyes focusing a little more (but not by much) and Red started to move into him at a steady rate, his thumb massaging the core of the slick blue heart.

                Sans focused on the mirror for a moment, his mind too far gone now to be too embarrassed by what he saw. He knew Red was watching him through the mirror, and that sent a different sort of shudder through him, and it was still odd to watch himself in such a position; it was almost like an outer-body experience, but the hand on his soul and the cock thrusting inside of him were all too real to disassociate.

                “You are unbelievably hot,” Red murmured. “Your soul is absolutely dripping, you’re so tight around me, and look at that gorgeous face, so overcome with arousal and need. Hmm, I want to make you come so badly.”

                Red slowly reached down and started stroking Sans with his free hand, dragging another strangled cry from Sans. He increased the rhythm, pounding into Sans harder, rubbing his soul harder, driving him to his edge.

                Sans glanced at the mirror one more time and it all became too much. His climax came suddenly, his body thrashed for a moment before tightening as his cock released his cum, spilling over Red’s hand. His soul felt like it burst, and he felt warmth filling him as Red came as well, groaning into his ear.

                _Too… much…_ was the last thought that fired across Sans’ mind as his eyes rolled back once more and he passed out.

                Red tightened his hold around Sans’ limp body. “Whoops, heh, guess I overdid it. But, fuck that felt good.”

                He carefully let go of Sans’ soul and gently helped him lie on his front, head nestled comfortably in the pillow while Red undid all of the ropes and set them aside. He moved Sans back to the head of the bed and made sure he was comfortable before pulling a sheet over him and dropping a kiss on his slightly opened mouth.

                Red took the next few moments to clean up; the ropes and mirror were put away, a towel was laid by the foot of the bed where they had made a mess, Red had a washcloth ready for when Sans came back around as well as a bottle of water. He climbed back into bed, sitting back against the headboard and pulled Sans over to cuddle him, stroking his skull as he began to come back to the waking world.

                “R-red?” Sans murmured.

                “Hey, welcome back,” Red said. “How did you like it?”

                “I’ll tell you when my head stops buzzing, but I feel wonderful,” Sans said, smiling up at him.

                Red reached over for the water bottle and handed it to Sans. “Here, this should help.”

                Sans nodded gratefully and drank about half of the bottle before giving it back to Red, who took a swig himself before setting the water aside.

                “The mirror thing was a bit much,” Sans murmured, almost burying his face into Red’s shoulder. “That was embarrassing.”

                Red curved his hand around to Sans’ cheekbone and lifted his head to look at him. “Well, so is sex, at first. I just wanted you to see what I see. I’m still kind of getting used to it myself, though, I have to say it’s a little less embarrassing when you’re top.”

                “If I wasn’t completely sapped of my energy, I’d fuck you right now to see for myself,” Sans muttered.

                Red chuckled and kissed Sans. “I bet you would.”

                “How many other kinks are you hiding, anyway?”

                “Want to take a shower and find out?”

                Sans sighed. “Red, you’re going to be the death of me.”

**Author's Note:**

> Come visit me on [Tumblr!](https://soloshikigami.tumblr.com/)


End file.
